With the development of electronic industry, electronic waste recycle industry is taken more seriously than ever. Many companies invest more capital, in order to enhance the efficiency of recycled metal, and its purity. For the recovery of noble metals, such as gold-plated printed circuit board, gold finger, FPC, lead frames, and components, etc., the gold can be recovered and re-used.
As is well known, gold is one of the noble metal with high chemical resistance. It is not easy to dissolve or corrosion by acid or alkaline solution. Therefore, the traditional stripping gold (or gold dissolution) technology can only be applied by using aqua regia or cyanide. The main processes as following:
For aqua regia, its advantages may be considered as easy to prepare, and could dissolve most of metals. However, with its strong corrosive, the potential risk is quite huge for all operators. Protective equipment need to be applied mostly.
On the other hand, using cyanide as gold stripper, unfortunately, always produces cyanide-containing waste, which contains huge wastewater, high cyanide content, and few amount of heavy metals. The waste water must to be diluted 500 times before its recycle process, so it actually increases water consumption and operation cost. Besides, few amounts of heavy metals cannot be recycled as mixed sludge. Especially, in the stripping processing, it is easy to produce cyanide with volatile and toxicity. When cyanide contacts skin, it will prevent oxygen exchange of human tissue cells, resulting in cell death. Therefore, it is very harmful to heart and brain. The cyanide is regulatory in nature highly toxic substances, and it may harm the operator by the slightest mistake.
Besides the damages of human body as we applied above, the gold stripping methods by using aqua regia or cyanide-based chemical components would also damage the electronic parts as connector's substrate, especially would he completely destroyed by aqua regia. This phenomenon makes the re-work of defectiveness become impossible. Although the gold from those electronic, parts can be recycled, the rest of parts of these products have to be re-manufactured. In addition, those two existing gold strippers not only need to be improved of their reaction rate, but also the amount of gold dissolution.
In summary, this invention attempts to provide a non-cyanide gold stripping technology, which owns especial characteristics as environment friendly, human body safety, better gold stripper rate and dissolution amount, compared to aqua regia or any cyanide-based chemical component.